Cliffs Used as Communal Roosts by Andean Condors Protect the Birds from Weather and Predators

Abstract

The quality and availability of resources influence the geographical distribution of species. Social species need safe places to rest, meet, exchange information and obtain thermoregulatory benefits, but those places may also serve other important functions that have been overlooked in research. We use a large soaring bird that roosts communally in cliffs, the Andean condor (Vultur gryphus), as a model species to elucidate whether roost locations serve as a refuge from adverse weather conditions (climatic refuge hypothesis, CRH), and/or from predators or anthropogenic disturbances (threats refuge hypothesis, TRH). The CRH predicts that communal roosts will face in the opposite direction from where storms originate, and will be located in climatically stable, low precipitation areas. The TRH predicts that communal roosts will be large, poorly accessible cliffs, located far from human-made constructions. We surveyed cliffs used as communal roosts by condors in northwestern Patagonia, and compared them with alternative non-roosting cliffs to test these predictions at local and regional scales. We conclude that communal roosting places provide refuge against climate and disturbances such as, for instance, the threats of predators (including humans). Thus, it is not only the benefits gained from being aggregated per se, but the characteristics of the place selected for roosting that may both be essential for the survival of the species. This should be considered in management and conservation plans given the current scenario of global climate change and the increase in environmental disturbances.

Why geodiversity matters in valuing nature's stage

“…This limits plant life to species that can cling to rocks and soil-filled crevices and animal life to species that can fly or climb very well. For both plants and animals, cliffs offer protection from some predators and competitors and this means some species (e.g., grazing-intolerant plants in areas otherwise subject to extensive grazing by domesticated animals) are usually found only on cliffs (Lambertucci & Ruggiero 2013). Cliffs also allow some species to reach extraordinary densities (e.g., thousands of seabirds nesting on a small cliff face [Larson et al 2005]).…”

Birds in rocky habitats of the Tatra Mountains (Carpathians): species diversity and multiple ecological relationships

“…These species, locally associated with rocky habitats, made nests on rocky ledges, and their territories included cliffs and inaccessible rocks which could be continuously occupied for long period, highlighting the great importance of this type of nesting site (Ciach 2005;Ciach and Czyżowicz 2014). Rocky environments may be used as communication or roosting sites (Stille et al 1987;Brown andPiper 1988, Lambertucci andRuggiero 2013). Apart from enhancing biodiversity, rocky environments also increase the diversity of ecological relationships.…”

“…The inaccessibility of nesting sites could be one of the major drivers of habitat selection (Rodríguez et al 2013) and could be a (Amato et al 2014). For individual birds, they provide shelter from unfavourable weather conditions and disturbance, but communal roosting sites among cliffs are also important for social species, which need safe places where they can meet and exchange information (Lambertucci and Ruggiero 2013). In rocky environments, species that generally nest in habitats other than rocks reveal their ecological flexibility.…”

Meteorological and environmental variables affect flight behaviour and decision‐making of an obligate soaring bird, the California Condor Gymnogyps californianus

“…obs.). Likewise, Andean Condors Vultur gryphus also choose roosts that provide refuge from potential predators (Lambertucci & Ruggiero 2013). Thus, Condors and other obligate soaring birds face weather-related trade-offs that balance time, energy and risk costs with pay-offs such as food or safety during their movements (Harel et al 2016).…”